Synthesis and Structural Characterization of the First Thermally Stable, Neutral, and Electrophilic Phosphinidene Complexes of Vanadium

Abstract

The first thermally stable, neutral, electrophilic phosphinidene complexes of vanadium, [CpV(CO)3{η1-P(NR2)}] (R = iPr (3a), Cy (3b)), have been prepared by the reaction of [Na]2[CpV(CO)3] with Cl2PNR2. The molecules 3a and 3b have been characterized by microanalysis, IR, and 1H and 31P{1H} NMR spectroscopy, and for 3a also by single-crystal X-ray diffraction. The structure of 3a exhibits a piano stool geometry closely related to that of CpV(CO)4 with an η1-phosphinidene ligand replacing CO in one of the basal coordination sites of the vanadium atom (V(1)−P(1) = 2.300(2) A). The reactivity of 3a toward a variety of unsaturated substrates: PhC≡CPh, di-tBu-imidazol-2-ydene, PhN3, and Ph2C═N═N has been examined to probe the electrophilic (or nucleophilic) character of the low-coordinate P(I) site. In all cases reactions occur exclusively at the phosphinidene phosphorus atom, without CO displacement, affording examples of P-coordinated phosphirene [CpV(CO)3{P(NiPr2)CPh═CPh}] (7), abnormal NCN carbene adduct [...